Liquid-level gauge



Jan. 13. 1925.

M. B. FIELD LIQUID LEVEL GAUGE Filed Jan. 14, 1921 2 Sheets-Sheet 1 wiwi m 16 @M Jan, 13. 192.5.l 1,523,10

M. B. FIELD LIQUID LEVEL GAUGE Filed Jan. 1,4., 1921 2 Sheets-Sheet z IIII lil

A k LL simple embodiment. of the invention.

Patented jan.. 13, 1925.

UNITED 'STATES Partnr orFicI-z.

MICHAEL BIRT FIELD, OF GLASGOW, SCOTLAND, ASSIG-NOR TO PNEUMERCATOR COM- PANY, 0F NEW YORK, N. Y., A CORPORATION OF MAINE.

LIQUID-LEVEL GAUGE.

Application led. January 14, 1921. Serial No. 437,301.

To all whom t may 00m-era.'

Be it known that I, MICHAEL BIRT FIELD, a subject of the King of the United Kingdom of Great Britain and Ireland, and residing at Glasgow, Scotland, have invented aV certain new and useful Improvement in Liquid-Iievel Gauges, of which the follow ing is a specification.

This invention relates to an improved apparatus for ascertaining at a distant station the position of the plane of demarcation between two immiscible liquids in a tank or other vessel filled with such liquids, or for ascertaining the weight, height or volume of either or both liquids in the tank orothe-r vessel, or the total weight of the liquid contents of such tank or vessel.

For the purpose of explanation I shall describe the invention as adapted for ascertaining the position of the plane. of demarcation of fuel oil and sea water contained in a compensated fuel tank in a submarine having provision for admission of sea water to take the place of fuel oil as the latter is expended. I shall further vassume that the fuel oil is lighter than sea water or occupies the upper portion of the tank.

The invention involves the application of vthe principle disclosed in the Specification of Letters Patent No. 1131412 in which the measurement is effected by a measurement of the air pressure necessary to force the liquid out of an immersed balance chainber or chambers.

In the accompanying drawings Fig. 1 is a diagrammaticV elevation showing 1pile tig. 2 is a diagrammatic elevation and Fig. 3 a plan of a modification. Figs. 4 and 5 are diagrammatic elevations showing two further modifications.

In the embodiment of the invention shown in Fig. l there are employed two balance chambers l, 2 at the same level, both chambers being located within thetank 3 near the upper end thereof and with their orifices approximately level with the fuel draw-off pipe F, the chamber l being open to the interior of the tank 3 and the chamber2 open at its bottom to the sea-water outside the tank.

From the chambers l, 2 are led tubular connections 4, 5 to the ends of a di'erential gauge 6 having cocks 7, 8 one on each side with air connect-ions, not shown, and constructed and arranged to operate substantially as described in the specification of Letters Patent No. 3.131412. "The gauge 6 serves in effectto measure the difference of head of a column of sea water equal in height to the height of the balance chamber oriices above the bottom of the tank and of vthe column of sea. water and oil below the orifice of the balance chamber 1 as it exists in the tank.

The conclusion above stated follows from the fact first that the gauge 6 indicates the difference between the pressures existing in the two balance chambers, and second that these pressures differ from one another according to the height of the plane of demarcation. The pressure in the balance chamber 2 is that due to the depth of sub mergence of the inlet to this chamber below the surface of the sea, and is less than that at the bottom of the tank by an amount equal to the head of a column of sea water equal in height to the vertical distance from the bottom ofthe tank to the orifice of the balance chamber; while the pressure in the balance chamber l is equal to that due to the depth of submergence of the bottom of the tank 3, less the pressure of the layer of water in the tank, and less further the pressure of the layer of oil superposed on the water layer. Hence the diferenoe between the pressures in the two balance chambers is that expressed above. Evidently when the tank is full of oil, the difference is a maximum, and when it is full of water the difference vanishes. The position .of the gauge indication between zero and the maximum is, therefore, a measure of the height of the demarcation plane.

In the modication shown in Figs. 2 and 3 both balance chambers 1, 2 are located outside the tank 3', the chamber i having a connection to the interior offthe tank 3 and the chamber 2, at the same level, being piped to the sea.

In other respects the arrangement shown in Figs. 2 and 3 agrees with that shown in Fig. l.

The embodiments shown in Figs. l to 3 are based on the principle of measuring the difference of fluid pressure of a column of sea water equal in height to the tank and of f gravity of sea water S1, and thatof Ythe oil S2, we may otherwise express the said pressure difference as the"`-fl'uid" pressure of a column of fluid of' height B and specific g'raafity (Si-LSL). Y

To effect measurement by theapparatus shown in :Figs: "1 'to 3 a knowledge of" the -VPhe difference S14-b2' may be small in comparison with S1 and S2, as, for example, when oil of specific gravityof' 0.95 is enr ployed,"in which event a small change in Sl orSQ" produces alarge relative change in (Sli-S2) and the resulting measurement is correspondingly affectedf This drawback is overcome by the modifications now' to be described.

`nthese modifications I'` provide two or more ina'nometers preferably of the fluid column type, which indicateat least two of the following pressures:v that of' a coluinnotl height A and specific gravity S1-S2, that of acolumn of height B andfspecitic gravity Sl-Sgy 'that of aV lcolumn' of known height, which may be that of the tank, and of specific gravity Sl-SZ. Any two of these measurements are sufficient f'or the determination ofA and B, the tank height being offf'course known; the result being independent of the values of S1 and S2.

7 In the modifications shown in Fig. l I provide insidethe tank 10 two staiidpipes 11; 12 extending fromthe bottom to` the top.v The lower` ends of these ystandpipes are closed, andtheir upper ends are in communication with tlleltank contents. The standpipe 11 istilled with sea water or fluid of the' same specific t gravity as that of the layer A; the pipe 12 is filledwith oil constituting the layer B.

" Thepressures existing at the lower ends of the standpipes *11, 12 as also the pressure at thebottom ofthe tank 10 are transmitted by gaseous medium such as air to the limbs of a 3-legged U-tube lfcontaininga suitable quantity of liquid, 13 denotes the leg connect'e'd't-o `the sea water column; 132` denotes the` leg to which the oil column is connected; the leg 133`is connected to the tank. It will be evident that the liquid in the three legs will stand at various heights such that the dif'terence'of height of the columns 133 ,and 3 represents the height B, and the difiere enceof 131V and 133 represents the height A l tov the scale in Which A-B or` the tank height is represented by the difference of 132 and P13', Y

(S1S) while the difference/lof 1 3,3 and 13 represents the pressure `headBr(Si-'=S2).` The reasons for the conclusions last stated may be briefly explained thus. V `The pressure exertedon the leg lsgwfrom the balance chamber to which said leg is connected is that due to the depthof submergence of' the entrance from the tank to said balance chamberg? in this case assumed toV be the tank bottom. y Y i Then the pressure exerted on the leg 13* is equal to the same pressure', lessthe pressure of the Water layer A, less ythe pressure of the oil layer B, plus the column of 'oil in the standpipe 1Q. Since the pressure due to the depthot submergence acts equally on both legs, it cancels out when differences are considered; and sinceV the oilrlayer B outside the standpipe balancesan equal height of oil in the upper part of' the'jstandpipe the net pressure difference is that between the layer A 'of water and a column of'oil of thesame height.- The layers of" oil and water in the tank transmit the pressure due to submer genceto the top of the columnin the-stand# pipe; but "as theselayers have weight themj selves they diminish the pressure transmitted bythe amount due to their respec-V tive heights and" specific gravities.4 j

By like reasoning the pressure transmitted tothe leg 18'* is seen to`be thatdue vto the depth of submergence of' thebottom off-:the tank, less the pressure of the waterlayer A, less'the pressurcof oil layer B, and plus the pressure of' the water column in' the stand# pipe 11." The pressure due toY submerge'nce acting on both legsl'l 'and A133 cancelsout, and the column of water in the standpipe up to'thedeinarcation planebalances theV layer Aj of water foutsidefthe standpipe, l

leaving as the effectiv'efpressure difference only' that-between the column :of water in the'fstandpi'p'e of height Bj and the layer of oil in the tank of height'll. Between the legs 13 and 132. the pressure difference is f-`- quite obviously the Y difference between the water column in the standpipell of height A plus B and the oil column in standpi'pe 12 of the same height. Y' l* 1f" anyl variation-shouldoccur `in the specific gravity' of either liquid," without `any change in the height'fof` the'deinarcation plane, Vthe heightfof the Iindicating`columns wouldchange But in everycasen the portion 'ofthe gauge column differences A and .'B to theheightsofthe layers A and B, respectively, in thentank "will remain the sameyand the diflerenceA plus B between ,the columns in the'legs'l andV 15?-i's the measureof 'the tank;l height, no matter what the``l absolutev value 'of f this'columnditierence may happen to be; whereforetheposition of arm-,grama ,inl-21a# beavtagr-as eventi' ,the f f A (S1-S2) represents the change of weight per unit of tank cross sectional arcacompared with the weight when the tank is full of oil. Thus by applying suitable calibration scales to the column differences 1233-13 and/or 132-133 measurements of the change of weight of tank contents may be made as oil is replaced by water or vice versa.

In the construction shown in Fig. 5 I em- Y ploy two manometers or gauge tubes 14;, 15,

and three standpipes 16, 17, 1S. The standpipes 1G, 17 preferably to the height of the tank 19 are filled respectively with sea water and with oil. These are open to the atmosphere in the submarine or other vessel at their upper ends The standpipes may enter the tank through liquid-tight joints so as to be immersed in the tank conte-nts for the greater part of theirlength and thus provide for equality of temperature conditions. Y n

The standpipe 1S filled with oil is con tained wholly within the tank, being of a length approximately equal to the tank height, and open at the upper end to the tank contents. Y

The pressures at the lower ends of the standpipes 16, 17 are transmitted by air medium to the manometer 14, so that it indicates the difference of such pressures, and the pressures at the bottom of the standpipe 18 and at the bottom of the tank 19 are transmitted to the manometer 15 in like manner, so that it also indicates the difference of said pressures.

The manometer 15 then indicates the height of Vthe water layer A to the same scale as the manometer 14 indicates the tank height.

It will be understood that the manometer column 15 represents the pressure head A (SlsSz). Thus, as explained heretofore, by applying a suitable calibration scale to the manometer 15, the change of weight of the tank contents as oil is drawn off and replaced by water may be indicated and measured.

Various means may be employed to flood the standpipes.

It is important that the Huid contents of the standpipes shall be of the same specific gravity as the water and oil in the tank.

The standpipes 1G, 17 may be interconnected, as shown, above the level of the water column and a small excess of oil may be added so as to prevent evaporation of the water column. The pipes being interconnected, the free oil level will be the same in each and the excess will not introduce inaccuracy.

A pet cock 20 may be provided in the standpipe 16 for the purpose of ensuring that the water stands at the desired level.

In Figure the standpipe 1S is equivalent to the standpipe 12 shown in Figure 4; but any equivalent of the standpipe 11 iilled with water and exposed to the pressure existing in the tank is omitted; however, the latter column may be applied to the modification shown in Figure and connected with a differential gauge otherwise the same as Y the gauge 15, or combined with a three legged gauge as shown in Figure 4.

Either of the means shown in Figures 4 and 5 for ascertainingthe difference between the specific gravities of the two liquidsmay be applied to the particular combination shown in Figures 1, 2 and B with essentially the same effects as described in connection with Figures et and 5.

For the purpose of the above description it has been assumed that the oil is lighter than water. lVhere the converse is the case, the necessary inversions may be introduced without departure from the spirit and principle of the invention.

For simplicity of explanation the liquids are herein referred to as water and oil. The invention is equally applicable, however, for ascertaining the position of the plane of demarcation between other immiscible liquids.

In intances it is fo-und that a quantity of water is present as a layer at the bottom of an oil tank, where the remainder of the tank may be only partly filled with oil and it is desired to ascertain the depth of such water layer. It will be understood that the methods hereinbefore disclosed permit of the measurement of A (S1-S2) while a subsidiary gauge connecting to two stand pipes of known height filled with water and with oil, respectively, will provide a measurement of (S1-S2) where K is the known height, so that A is determinable by comparison.

I claim 1. The combination with a tank filled with two liquids which 'are non-miscible and are of respectively different specific gravities, and being under pressure from an external source of one of the liquids tending to enter the tank, of an apparatus for indicating the height of the demarcation plane between the liquids, comprising a differential gauge, pipe lines containing 'a gaseous medium and so connected with said gauge that the latter is caused to indicate the difference between the pressures existing in the diEerent lines, and balance chambers connected to the terminals of the lines, one of which chambers is in communicationv with the tank at a point due to the pressure imposed at the bottom of the tank by the external pressure n'iinus the Weight of the tank contents, while the other is .exposed to the vsaine pressure less the Weight of a column ofone of the liquids ot' al height substantially equal to that ofthe tankfcontents. Y

2. .The combination with a tank filled with two liquids of different specilic gravities which are non-iniscible and are under pressure from an external source ot' one of the liquids tending to enter the tank, of means for ascertaining the position of the plane of demarcation between such liquids, including standpipes each extending vsubstantially from top to bottoni ci' the tank and each containing one of the liquids exclusively, balance chambers in communication respectively With each of said standpipes and with the contents ol" the tank at 'a level near the bottoni of the tankpipe linesV adaptedto contain a gaseous medium running from each of said balance chambers, and pressureresponsive gauges to which said pipe lines are so connected, that the pressures confined in the respective lines actin opposition to one another upon the gauges. The Combination with a vessel filled with iinniiscible liquids of respectively dii ferent specific gravities, under the pressure of one of such liquids tendingrto enter the vessel, of balance chambers at the-same level, one of which is open to the liquidcontents of the tank and the other to a separate body Where the pressure imposed thereon is that of one of the-liquids, means 'separating said body otf liquid from the conte-nts of thetank,

a differential gaugeco-nstructed to indicateV .Y

the difference between two pressures, and pipe lines adapted yto contain a gaseouspresed to s'aid gauge in a manner causing their contained pressures tojbe exerted-'in oppo-V sition to one another att/lie gauge.`

4. F or ascertaining the posi-tion of the plane'oi demarcation between twoVnon-mis# cible liquids oli-different specific giavities in apparatus including diilerential pressure 40 sure transmitting` medium, 4 extending from the respective Abalance chambers and connect-V -a vessel which isffilled by such liquids, an

gauge elements, 'a balance chamber open to sures differentially on saidgauge elements,

In'testimony whereof I have signed my n'a-me to this specification in the presence ofV two subscribing Witnesses. Y

Y MICHAEL BIRT FIELD.

Witnesses Y ISABEL RoLLo, FLORENCE HOUSTON. 

